The present invention relates to a member for supporting an EMC (electromagnetic compatibility) ferrite core.
Conventionally, for EMC use of devices, an EMC ferrite core has been widely used for preventing unintended electromagnetic radiation, which causes noises in electronic devices such as medical devices and OA appliances. In particular, cables that connect such electronic devices with external devices can be transmission channels of noise components. Thus, typically, at proximal end portions of the cables, which are connected to circuit boards, the EMC cores are used. The EMC cores are very important for preventing the noise components. However, they require dedicated securing structure, and the securing position inside the electronic devices is limited.
FIG. 3A is a perspective view showing an inner structure of a circuit unit 90, which is provided at a proximal end portion of a scope unit 50 of an electronic endoscope shown in FIG. 4. On a printed circuit board 89 inside the circuit unit 90, a CCD driving circuit for supplying driving signals to a CCD provided at the distal end of the scope unit 50, and a signal processing circuit that processes the output of the CCD are provided.
The external connector 81 is used for connection with a processor unit, which processes the output of the CCD and generates a video signal. Through cables 86c and 87c connected to connectors 86 and 87 on the printed circuit board 89, the processor unit is connected to the printed circuit board 89. The processor unit accommodates a light source, which emits light to a light incident portion 80. The light is directed through a light guide 75 to the tip end of the scope unit.
A cable 88c, which is connected to a connector 88 mounted on the printed circuit board 89, is a cable including a bundle of signal transmission wires connected to the CCD, which is provided at the distal end portion of the scope unit. In some cases, an insertion portion 51 (see FIG. 4) of the scope unit is several meters long, and the signal cable 88c also has the same length. In order to prevent unnecessary radiation of electro magnetic wave inside the circuit unit 90, the signal cable 88c is inserted through EMC cores 77 and 78. The EMC cores 77 and 78 are secured inside the circuit unit 90. For this purpose, as shown in FIG. 3B, which shows a cross section taken along line Cxe2x80x94C of FIG. 3A, the EMC cores 77 and 78 are screwed on a side wall of a casing 100 using a supporting member 79. The circuit unit 90 is covered with a shielding cover 82 made of metal, which prevents unintended radiation of an electro-magnetic wave from the printed circuit board 89.
As described above, an EMC core supporting structure is a dedicated structure for supporting EMC cores inside a device, and does not have shielding and/or heat radiation functions. Further, a position where the supporting member is mounted inside the electronic device is limited. Therefore, using an EMC core may impede design freedom and/or sometimes prevent downsizing of electronic devices.
The present invention is advantageous in that an improved structure for securing an EMC core and a securing member used in such a structure are provided, which prevents radiation of electro-magnetic waves from devices, allows for radiation of heat, allows for downsizing of the devices, and provides improved design freedom.
According to embodiments of the present invention, there is provided an EMC core supporting structure for supporting at least one EMC core inside a casing which accommodates a printed circuit board mounting at least one heat generating element. The structure includes a shielding plate arranged on one side of the printed circuit board. The shielding plate is capable of shielding electro-magnetic waves. A plate member is capable of shielding electro-magnetic waves. The plate member is located on the other side of the printed circuit board, the plate member expanding inside the casing to substantially cover the printed circuit board. A supporting portion, which receives the at least one EMC core is formed on a surface of the plate member opposite to a surface facing the printed circuit board for mounting the at least one EMC core, the surface of the plate member facing the printed circuit board contacting the at least one heat generating element, the printed circuit board and the plate member being fixed with each other.
With this structure, an EMC core supporting structure is capable of preventing radiation of electro-magnetic waves from a printed circuit board, allowing for radiation of heat, allows for downsizing of the devices, and provides improved design freedom.
Optionally, the at least one heat generating element is secured on the plate member.
In a particular case, the at least one heat generating element is electrically connected to the plate member through lead lines, at least one heat generating element being detached from the printed circuit board.
Optionally, a spacer is provided between the plate member and the printed circuit board.
According to an embodiment, the EMC core supporting structure includes a casing. The surfaces of the casing, which do not face the one surface and the other surface of the printed circuit board, have a shielding function of preventing transmission of electro-magnetic waves.
Optionally, the casing is made of metal, and the plate member may be electrically connected with the casing through the connection portion. Alternatively, the casing is made of metal, and the plate member is electrically insulated from the casing.
In an embodiment, the EMC core supporting structure may include a casing, and the plate member is formed to have a connection portion that is secured onto the casing.
In a particular se, the plate member may include a portion that is bent to form an L-shaped portion, which is secured onto an inner wall of the casing.
Optionally, the L-shaped portion is secured on the inner wall using screws.
In an embodiment, an EMC core supporting element is integrally provided on the supporting portion of the plate member, the at least one EMC core being held by the EMC core supporting element.
In this case, the EMC core supporting element may include a U-shaped portion having two parallel surfaces and a connecting portion that connects the two parallel surfaces, the connecting portion being secured on the plate member, the at least one EMC core being held within a space defined by the two parallel surfaces and the connecting portion.